1. Field of the Invention
This invention is concerned with harvesting machines and the crop gathering reels of harvesting machines. More specifically the specification deals with means to control the elevation of the reel so that each end of the reel moves in unison with the other end.
2. Description of the Prior Art
In a harvesting combine the combine may be equipped with a forward mounted crop gathering and cutterbar head. The cutterbar will usually be designed to follow the contour of the supporting ground while a reel, being the crop gathering component designed to bring the crop to the cutterbar and minimize grain losses, will be mounted above the cutterbar and move upwardly or downwardly generally following the position of the cutterbar. Also, the reel can be operated independently of the cutterbar, that is, the vehicle operator can raise or lower the reel at his discretion.
The reels of contemporary machines are raised and lowered through the pressurization and evacuation of a pair of hydraulic cylinders located at the ends of the reel. Typically the arrangement is a master-slave arrangement where one of the cylinders is a double acting cylinder and the other is a single acting cylinder. When the master cylinder (the double acting cylinder) is pressurized on the head side fluid in the rod side of the cylinder is pressurized and forced to the head side of the single acting cylinder causing both cylinders to extend simultaneously in a well known manner.
The difficulty in having the master-slave cylinder arrangement is that the master and slave cylinders are often of non-standard nominal diameters. With excellent engineering and design a passable reel lift system can be manufactured but size and capacity considerations are critical. With even well designed master-slave systems rephasing of the cylinders so that the ends of the reel move in unison requires special orificing and porting for the rephasing operation. In some designs rephasing requires manual venting to synchronize the cylinders.
Spool type flow divider systems are also known to be used as alternatives to master-slave cylinder systems. With spool type flow dividers the work port of each cylinder is in direct communication with the other thus making the synchronous displacement of each cylinder's piston difficult as the piston with the least resistance will tend to extend at a rate different than the cylinder with the higher resistance. Thus although the flow is divided the reel ends may not always raise in unison as will be assured in the present invention.
The contemporary prior art system requires more parts, more expensive cylinders and more complicated hose routings (increasing the risk of leakage) than the system presented by this disclosure.